The present invention relates to a novel vision screening system. More particularly, the present invention relates to a method and related apparatus for detecting eye disease that may be easily and conveniently administered to a test subject without the need for trained personnel or specialized equipment not readily available outside a medical office.
Glaucoma and diabetic eye disease are prevalent afflictions of the eye that can occur in anyone at any time and can lead to permanent loss of vision. By far, the most common type of glaucoma is chronic simple glaucoma which is painless, slowly progressive and virtually undetectable by the individual particularly in its stages when it is most easily and successfully treated. Most individuals with glaucoma only become aware of it at a time when all that remains in one or both eyes is tunnel vision due to its gradual, painless and progressive course when left untreated. The same is true for other diseases associated with abnormalities of the field of vision, including but not limited to diabetic eye disease and certain brain tumors.
With normal peripheral vision, at any given distance from the eye, a blind spot exists at a predetermined distance just temporal to a target point at which the eye is fixated. Most of the earliest scotomas in glaucoma (i.e., small circumscribed areas ranging from dimness to completely blacked-out areas of visual field) occur in a narrow region radiating generally arcuately from just outside this blind spot above and below the point of fixation. Advanced glaucoma changes are present when multiple scotomas in this region begin to coalesce after which they extend beyond the region itself and eventually encroach on or eliminate central vision. Prior to actual loss of central visual acuity is a nonspecific decrease in central vision contrast discrimination. In early diabetes, areas in close proximity to the foveal vision develop discrete areas of tissue damage leading to receptor dysfunction or failure, often coalescing due to fluid leakage draining according to anatomical channels towards the foveal vision. Typical to early diabetes then are areas surrounding the central visual field, usually within a 10 degree cone angle, with discrete areas of tissue damage and dysfunction. These areas can continue to dim, surrounding sharp central vision, soon affecting central contrast vision, until eventually the central vision and its best acuity itself are reduced.
Most of today's methods of visual testing for peripheral vision loss from glaucoma and other diseases require sophisticated devices to accurately create a peripheral vision map, which is a graphic depiction of the extent of the field of vision, with any areas in which peripheral vision is diminished or absent well demarcated. These tests require specialized equipment, use of a trained technician, and have associated with them the problem of maintaining fixation. That is, in order to test peripheral vision, the test subject must maintain focus on a central target; failure to do so invalidates that particular peripheral vision testing sequence, and if occurring frequently enough, invalidates the accuracy of the test.
In addition, since these tests are not self-tests, the diabetic field of vision test, known as a macular, or 10 degree field of vision test, is rarely used, with preference for angiographic study of the retinal circulation, the retina being the affected tissue layer at the back of the eye in diabetes. A self-test assessing the health of the visual field as well as foveal vision could allow early awareness of diabetic eye disease within the home, prior to the permanent loss of central vision which now is frequently the earliest warning sign one afflicted with the disease will have.
One of the peripheral vision tests which has long been used, the tangent screen, is a simple test, but it too has the same fixation problem and requires a technician. Other tests of this nature include manual and automated perimetry. These visual field tests also require a technician to administer the test, and use highly specialized equipment. The patient looks at a central fixation target within a hollowed-out dome, and indicates when a light can be seen with side vision. While these tests can be very accurate, they are often difficult to administer properly since they are tedious--often taking twenty minutes or more per eye--and it is difficult to completely prevent the patient from looking directly at the source of light which is the peripheral target rather than remaining fixed on a central target and using side vision to detect the light. A trained observer views the test taker's pupil, and warns the test subject when movement of the eye is observed--the standard means of trying to maintain fixation. Such tests also typically require the use of special equipment that tends to be rather large and bulky.
About one person in five with normal visual health is unable to adequately follow the instructions discussed above to provide for useful test information. This translates to nearly one person in three in a population of glaucoma patients, where such testing is especially important for both initial diagnosis and monitoring. Of the millions of Americans at risk for glaucoma, only a relatively small fraction of this population is seen by eye professionals in a given year, and only a portion of the individuals who obtain professional assistance receive such sophisticated testing. Diabetic eye disease and glaucoma, the two leading treatable causes of blindness, are frequently first discovered after vision loss becomes sufficiently advanced to have caused permanent noticeable vision loss. Due to its gradual onset this may be misinterpreted as a glasses problem, and examination delayed. Too frequently, by the time diagnosis and treatment begins, considerable irreversible damage exists in one or both eyes, and treatment is more difficult and less vision can be saved. Earlier diagnosis and intervention before vision loss is detectable by the human eye would greatly increase the successful treatment of these diseases, and decrease the need for complex surgical intervention that is required for advanced cases.
My U.S. Pat. No. 5,061,059 entitled "Self-Detection Glaucoma Test Method," which is incorporated into this disclosure by reference, describes a novel method test method for self-detection of eye disease. Indeed, the test method described in my patent is relatively easy and convenient to use without the need for expensive equipment or a technician.
An improved test method, however, might further enhance the ability to test for eye disease with improved accuracy, allow assessment of central as well as peripheral visual health, improve fixation compliance, provide testing instructions in a convenient manner, provide for self-demonstration, interactive test subject training, and interactive review of test-taking proficiency. Further, an improved test method might, at the same time, be easy to use, convenient, and relatively entertaining. It is therefore an object of the present invention to provide an improved eye disease self-test method that further enhances the ability to detect eye disease and is also easy to use, convenient, and relatively entertaining.
Other objects and advantages of the present invention will become apparent from the ensuing description.